Mobile devices are commercially available having hardware interfaces for connection to storage devices. Those storage devices can be used to store, for example, images or encoded audio data, for access and processing by the mobile device.
Mobile devices, for example mobile telephones, comprise a host processor which performs a number of tasks, for example managing wireless connections, providing a user interface and providing processing capacity for applications running on the mobile device. The host processor also interfaces with the storage device via an interface to access and/or store data on that device.
The host processor performs a number of functions, and is not therefore optimised for power consumption when performing any particular task. For example, decoding audio files utilising the host processor of a mobile telephone may drain the battery in a small number of hours.
Digital Signal Processors (DSPs) can be optimised for a specific task, and that optimisation very significantly reduces the power consumption for performing that task. The inclusion of a specific DSP for audio decoding in a mobile device may therefore lead to a significant increase in battery life when playing audio files. However, in order for the DSP to play audio files from a storage device, the DSP must access that storage device. During play-back, the host processor will still require access to the storage device and so a means to share the storage device between the two processors is required. If a DSP is utilised for performing certain tasks in a mobile device, it may also require the ability to write data to the storage device to perform its function.